Control actuator and control system



July 19, 1949., I v F, CLARK 2,476,584

CONTROL ACTUATOR AND CONTROL SYSTEM Filed Aug. 23, 1945 2 Sheets-Sheet i INVENTOR ATTORNEYS July-19,1949. F. G. CLARK 2,476,584

CONTROL ACTUATOR AND CONTROL SYSTEM Filed Aug. 23, 1945 2 Sheets-Sheet 2 INVENTOR ATTORNEYS I though not necessarily,

Patented July 19, 1 949 CONTROL ACTUATOR AND CONTROL SYSTEM Frederick G. Clark, Buffalo, N. Y., assignor to Eastman Machine Company, Bufialo, N. Y.

Application August 23, 1945, Serial No. 612,249

13 Claims.

This invention relates to actuators such as power operated actuators which comprise screw and nut membershaving screw-threaded engagement and act by the rotation of one member to move the other member axially or linearly for shifting or adjusting an associated movable control element or other device. Such actuators are used, for example, in aircraft, one screw member of the actuator being rotated by an electric motor for effecting required adjustments of a rudder, aileron, wing flap or other control element of the aircraft.

One object of my invention is to provide an actuator of the sort mentioned having an unidirectional operating motor, which, if desired, may run continuously, and by whicheither the screw or the nut member of the actuator may be driven to thereby produce motion by the actuator in either of opposite directions.

Other objects of the invention are to provide a screw actuator or jack screw of non-self-locking type in which either the screw or nut member may be rotated by the operating motor to effect axial or linear motion of one actuator member in either of opposite directions, or the rotating member is released from the motor in the event of failure of motive power, or may be readily so released when desired to permit free rotation thereof, and thereby enable manual operation of the actuator and the device which it'actuates; to'provide a screw actuator with electromagnetic clutch and brake means operable for coupling either the screw or nut member for rotation by the motor and holding the other member, or for holding both actuator members from movement in neutral position, or for freeing the actuator members to enable movement of the linearly movable member manually or independently of the operating motor; to provide an actuator of a construction enabling the efficient operation thereof by a uni-directional motor of low starting torque, such as an alternating current motor, or an under-powered motor of a kind that can be left running continuously with fly wheel effect, if required, to store energy for cycles of short duration; and to provide a power-driven screw actuator in which, in the event of power failure, brake means for the actuator members are instantly released, making the device immediately ready for manual operation.

Another object of the invention is to apply an actuator of the character mentioned as a power-operated booster in. a control system so as to enable the operator to perform the control operation either manually only, or by power, in such manner asto give the operator the feel or control of the operation, as in the case of a purely manual actuation of the control element.

Further objects and advantages of the invention will appear from the following specification of the preferred embodimentof the invention shown in the accompanying drawings, and the novel features of the invention are set forth in the appended claims. I

Fig. 1 is a view partly in side elevation and partl in longitudinal section, of a linear actuator embodying my invention.

Fig. 2 is an end elevation thereof.

Fig. 3 is a transverse sectional view thereof on line 3-3, Fig. 1.

Fig. 4 is a transverse, sectional view thereof on line 4-4, Fig. 1.

Fig. 5 is a diagram of the electric brake and clutch control system.

Fig. 6 is a more or less schematic view in side elevation illustrating the actuator as a booster in an aircraft control system.

Fig. 7 is an end elevation of the lever mechanism shown in Fig. 6.

In the preferred embodiment of the invention illustrated in the drawings, the actuator A comprises a screw member or screw-threaded shaft a and a nut member b which are relatively rotatable and through which nut member the screw member passes with screw-threaded engagement with the internal thread of the nut member. Preferably, these actuator members are rotatably mounted by arranging the nut member b to rotate and be held from axial movement in a suitable bearing l0, shown as a double end thrust ball bearing mounted in a suitable supporting frame ll. As shown, the screw a. is provided at one end with a suitable swivel head I2 for connecting it directly or indirectly, as through leverage means, with the device to be actuated, and the frame II is connected, as pivotally, by trunnions l3, with a relatively fixed bracket or part against which the actuator reacts in operation.

l4 represents a rotary element which surrounds and is adapted to rotate about the actuator screw in a suitable bearing l'5. This rotary element, which is preferably of annular spool-like form comprising a tubular body or sleeve provided at opposite ends with outwardly extending annular flanges Ma and lib, is rotated by a suitable motor 16 which is suitably mounted on the supporting frame I I and may drive the rotary element M, as by a pinion [8 on the motor shaft Ii meshing with gear teeth IS on one flange 14a of the rotary element. Preferably, the motor I is an uni-directional electric motor which may, if desired, though not necessarily, run continuously and thus rotate the rotary element [4 continuously in one direction, for transmitting its rotation either through the medium of a coupling member 29 to the actuator screw a or through the medium of a second coupling member ii to the nut b of the actuator. The coupling member 20 shown comprises a. central. shaft which extends into an axial hole in the actuator screw and has a splined or non-circular connection 2 with the screw which permits axial movement of the screw relatively to the coupling member 26, but causes the screw to rotate with the coupling member. Coupling member 20 has a tubular outer end portion 23 arranged to rotate in a suitable bearing 24 on the frame II and an annular flange or disk '25- projecting outwardly parallel with and adjacent to the outer face of flange Ma of the rotary element I4. The other coupling membertifiis shown as of tubular form arranged to rotate in a suitable bearing 26- on frame H and surrounds and has a splined or non-circular connection 21 with the actuator nut b, but causes the nut to rotate with it. Coupling member 21 is provided at one end with anannular flange or disk 28 which projects outwardly adjacent to and parallel with the outer face of the other flange 14b of rotary element l4.

30 and 3| represent two electric magnet clutch coils arranged in aniron or magnetic annular core 32 which surrounds the tubular body of the rotary member l4 and is suitably fixed inthe supporting frame Ii; W'hen electrically energized, the coil 39 sets up magnetic flux in the adjacent flange 14a of'the rotary element, and the other coil 3! sets up magnetic flux in the opposite flange "b of the rotary element, whereby energization of coil 30 acts to attract the disk 25 of the coupling member 20 to rotate with rotary element l4, and energization of coil 3| acts to attract the disk of the other coupling'member 2| to rotate with the rotary element. Thus either the coupling member 28 may be caused to rotate with the rotary element and rotate the actuator screw a, or the other coupling member 2! may be caused to rotate with therotary member and rotate the actuator nut 17.

Two electromagnetic brakes having coils 3-5 and 36 are provided, the one, 35, for holding the coupling member 29 and screw it from rotation when the nut b is being -rotated by operation of clutch coil 3|, and the 0ther,'36, for holding the coupling member El and nut from rotation, when the screw is being rotated by operation of the clutch coil 39. As shown, the brake coil 35 is arranged in a stationary magnet annulus 31 on the supporting frame I l adjacent the outer face of the disk 25 of the screw coupling member 20, and the other brake-coil 36 is similarly arranged in the stationary magnet annulus 38 on the supporting frame adjacent the outer face of the disk 28 of the nut coupling member 2!. When the brake coil 35 is energized, it will hold the coupling member 2:: and actuator screw it from rotation and permit axial movement of the screw in one direction by operating the clutch coil 3| to rotate the other coupling member and nut b; and conversely, when the brake coil 38 is energized, it will hold the coupling member 21 and nut from rotation, and permit opposite axial movement of the actuator screw by operation of its clutch coil 35 to rotate the coupling member 20 and screw 0..

Referring to the electric circuit diagram, Fig. 5, a power line 40 controlled by amain or override switch 4! is connected by branches 42 and 43 respectively with limit switches 44 and 44a, preferably single pole, double throw switches. One switch 44 in its normal position, shown in Fig. 5, closes the circuit from the power line through the brake coil 35 and energizes this coil to hold the coupling member 28 and actuator screw a sta tionary and,in its other position, opens this brake circuit and closes the circuit through a conductor 46 and the clutch coil to energize the latter and cause rotation of the coupling member 29 and actuator screw by the rotary element l4; whereas the other limit switch 44a, in its normal position shown in Fig. 5, closes the circuit from the power line through the other brake coil 36 to hold the coupling member 2| and actuator nut stationary, while'in the other position of this second switch 44a, it cuts out thebrake coil 36- tofree the actu'- ator nut b; andcloses the circuit through a con-- ductor 48 and the second clutch coil M to cause rotation of the coupling member 2| and actuator nut 12. When the actuator is in neutral or stationary, both switches 44, 44a are automatically held, as by spring action, in their normal positions shown, so that both brakes are energized and both the screw a and nut-b of the actuator are held from rotation and act to hold the device operated by the actuator from movement, whereas the operator, by throwing the switch 44, can deenergize the brake coil to release the screw and energize the clutch coil 30 to rotate the screw, thereby moving it axially or linearly in one direction; while by throwing the other switch 44a the operator can deenergize the brake coil 36 to free the actuator nut b and energize the second clutch coil 31 to cause rotation of the nut and thereby move the actuator screw a axially or linearly in the opposite direction. When the switch 44 is operated for rotating the screw a the other switch 44a remains in the normal position shown and energizes the brake coil 36 to hold the nut stationary, and vice versa, when the second switch 44a is operated to energize the clutch coil 3| and rotate the nut b, the first switch 44' remains in normal position and energizes the brake for holding the screw a from rotation.

In case of failure of the electric current, or whenever the operator desires to operate the control device manually, and simply opens the main or override switch 4| to cut off the current for such purpose, both brake coils will be deenergized and free the actuator screw a and nut b for rotation. The actuator screw a can then be moved manually in either direction by endwise pressure thereon in the desired direction and the freely rotating nut will permit such linear or axial movement of the screw and the control element which it operates. The jack screw or screw actuator is of a non-self-locking type in which the thread or screw connection between the screw and nut members is of sufilcient pitch or of such anti-frictional construction as to en'- able one member to be moved axially in either direction by end pres-sure there-on if the other member is released so as to be free to rotate.

Thus, the operator, by a simple actuation of one or the other of the limit switches 44 or 44a, can cause power or motor operation of the linearly movable member of the actuator in either direction desired, or by simple actuation of the main or overrideswitch 4|, can free the actuator members for manual operation of the linearly movable member of the device in either direction desired.

The improved actuator herein disclosed has various distinct advantages over existing actuators or systems, among which may be mentioned the following:

1. It permits the use of an uni-directional motor which can be left running continuously, if required, thereby eliminating excessive power surge caused by frequent starting and/or revers ing of the actuator motor.

2. It enables the use of a motor with low starting torque, such for example as an alternating current motor which has many desirable features, but due to its inherent low starting torque characteristics, has heretofore been impractical in many actuator applications.

3. This system permits the use of an underpowered motor of a kind that is operable with fly wheel effect to store energy for cycles of short duration.

4. In the described braking system for the actuator members, a non-self-locking jack screw can be used havin a high pitch or antlfriction screw thread arrangement, which has better mechanical efficiency than a jack screw of self-lock ing type.

5. In the event of power failure or, if required or desired by the operator, the brake means are or can be instantly released, and with the nonself-locking jack screw, the actuator is ready for manual operation.

A desirable application of an actuator of the character disclosed herein is as a power booster in a manually operable control system, as for aircraft and the like. Figs. 6 and 7 illustrate diagrammatically one such application of the actuator. In said figures, 50 represents a lever fulcrumed at and to which the manually operable pilot control stick is connected at 52, through the medium of a suitable leverage altering system (not shown), if necessary, for operating the lever manually. This lever is connected at 53 to a link 54 which is operatively connected to the element to be controlled. If it be assumed that fulcrum 5| of the lever 50 is a fixed fulcrum, we have a simple lever where the ratio of force applied to the work done is as the length 52"5l to the length 53-5l If by the use of such a simple lever arrangement one could get enough linear movement of link 54, the problem would be simple. But it so happens that the usual control surface must be moved a distance relatively great compared to the movement of the pilot's stick, so that the distance lost by the leverage gain is regained in the means illustrated in Figs; 6 and 7, by utilizing the actuator A to move the lever fulcrum 5] in the direction of the force exerted at 52 on lever 50. To accomplish this, as shown, the fulcrum 5! of lever 50 is movablyor shiftably mounted, as for example, by placing it on the free end of a second lever 55, which has a fixed fulcrum 5B, and the linearly movable member a of the booster actuator A is connected coincidentally to the lever 55 with the fulcrum 5|. The two limit switches 44 and 4441 are mounted on the lever 55 and are actuated by an extension 51 of the first lever 50. The movement of lever 50 about its fulcrum relatively to lever '55 may be limited, by stops 58 on lever 55 at opposite sides of the extension 51. When the lever 50 is moved manually in either direction about the fulcrum 5|, the switch for moving the actuator member a in that direction is thrown by the extension 51 of lever 50, and the actuator a will operate until it has advanced the fulcrum 5|, by movement of the lever 55 about its fulcrum 56, to the required position. When that point is reached, the extension 51 on lever 50 no longer presses on the movable switch member and the linear motion by the screw actuator A-cea'ses. This switch-operating movement of the lever 50 is limited by the stops 58, and when the lever extension 51 is in engage-' ment with either stop, the levers 50 and 55 act as a single lever of the 3rd class. The booster ratio is determined by the leverage applied by the combination lever Ell-55. The use of an actuating system such as described and illustrated in Figs. 6 and 7, for instance in an airplane for actuating a control surface, gives the pilot the feel of the varyingloads as the position of the surface is changed. That is an important feature of the described booster principle which a straight power system does'not have. T

The pilot or operator, by means of the main or override switch 4|, which may be located wherever most convenient for operation, can shutoff the current and cut out the power actuator and use manual operation. When the power circuit is broken, the actuator screw is freed for manual linear movement. as explained. The booster system disclosed, by the useof suitable lever ar-' rangements, can be made to give any desired booster ratio; r Referring to th'e'herein before mentioned use with the actuator of-an under-powered-motor with fly wheel effect, such a motor could be the conventional squirrel cage induction motor, the outer shell or stator of which is the stationary member of the motor. In such a motor, as is well known, the stator consists of a number of turns of copper wire wound into the slots in the core with the winding insulated from the core. The rotating member consists of a cylindrical iron core with a number of equally spaced holes run ning axially through the core slightly below the surface thereof. Solid bare copper bars are driven into these holes and at each end the bars are riveted into a copper end plate, so that the cop-' per and iron core are joinedtogether as a mass and are not insulated from each other. When the stator or wound member is energized, it sets up a magnetic field in the stator and an induced field in the rotor which causes its rotation. With such a motor, a fly wheel may be suitably con-' nected to rotate with the rotor.

However, in the motor with the fly wheel effect that is preferred for use with the herein disclosed actuator, the outer shell is the solid member with iron core and copper bars and the inner or cylindrical member is the wound part of the motor, and this wound cylinder or member is held stationary, and the solid outer shell rotates. This gives'the rotating mass a longer radius and con--' se'quently greater inertia without increasing the overall size of the motor and without materially increasing its weight. In other words, by using this type of motor, the eifect of an attached separate fly wheel is obtained from the motor itself.

I claim as my invention:

1. In a linear actuator having two members operatively connected for axial movement of one member by rotation of either member in the same direction, the improved construction comprising means rotatably mounting said members and holding one member from axial movement, brake means for separately holding either of said members from rotation, a uni-directional rotary driving element, and means operable to separately cobble either o a d, actuator members to s id.

dr vin eleme t or ota io h r i h whi e act: eating said bra e me ns to. ho d said o her meet-- her from rotation for moving one of; said actuator members a a ly in ne or n th r d c io In combinat n w h sc n nut em 12ers havin screwhr ded enga ment, means rotatably m untin aid screw and nut memb rs and holdin one mem e firom ax a mo eme a rotary dr ving elem nt clut h means for o tns said Screw mem e with said v n eleme eluteh means or ro a n aid no m ber w h said driving element, brake means for separately holding said screw and nut members from rotatier-1, and control means for said clutch and brake means operable to ca se rotation of eit r on or said screw and nut members by said driving element while holding the other of said members from rotation for causing opposite axial move,- ments of one of said members.

3. In combination. wit a jack cre co p i inga-screw member and a nut member having sorewthreaded enga ement, mean o tablv mountin said jack scr w mem rs and h l n one from axial movemen wh e p mi n xial movement of; the other, a r a y drivin le ent, clutch means for separately ro at n e t r f said jack screw members with said driving element in the same directi n r k ans or separately holding said jack screw members from rotati n; and control means for said clu ch and brake means operable o cause otat o of e t r iaok screw member by said driving member while holding the other member from rotation.

4.. In combination with screw and nut members ha screw -thread d enga ement, means ro tatably mounting said members and holding one member from axial movement while permitting axial movement of the other member. a rotary driving element rotatable in a single direction clutch means for separately coupling said screw and nut members to said rotary element for rotation therewith, brake means for separately hold-.1 ins .Saidscrew and n membe s from rotat on, and control means operabl oause said clu ch and brake means to rotate either one of said screw and nut members while holding the other of said members from rotation.

5. In combination with screw and nut members having screw-threaded enga ement, means rotatably mounting said members and holding one member from axial movement while permitting axial movement of the other member, a rota y driving element, a uni-directional motor for rotate ing said rotary element, clutch means for coo-s pling either said screw member'or nut member separately to said rotary element jor rotation therewith, brake means for separately h ld ng said screw and not members fr m o ation, and con ol means f r aid clutch and brake me ns ope able to ca se rotat on oi either of said screw an ot members while holdin sa d other o said m m e s from o tionl 6- combinat on with scre and not memb s havin eere tbr ad enga ement, m ans ro- 'tatably mounting said members and holding one memb fr m ax l m ement While permittin axial movement of the other member, a rotary element rotatable in a single direction, clutch means for separately coupling said screw and nut members to said rotary element ;for rotation therewith, brake means for separately holding said s r w and nut m m rs fr m rotat n, and. ont ans fo said clu ch and b ake means operable to cause rota ion of either one or aid screw an nu m mb s ha n crew t r ed screw and out members. b said r tary element whi e hold n t e the o sa d members from e tation, said control means being also opereble to. release bot e sc ew an t memb fro aid c utoha b k m n o permit relati e axial movement of said screw and nut members by axial pressure on one of said members.

1, In combination with rotatably mounted screw and nut members having screw-threaded encasem n a r ta d vi m n el t o clutch means for coupling said driving ole-i. ment to one of said screw and nut, members for rotating it, electric clutch means for couplin said driving element to the other of said members for rotating it, electric brake'means for holding one of said screw and nut member from rota-l tion, electric brake means for holding the other of said members irom rotation, and control means operable for simultaneously energizing the clutch means for either of said screw nut members to rotate it, and energizing the brake means for the other of said members to hol it i om ta on! 8, I ooinb ati n i sc a d t m mbers ha ng sc wh aded ngag en m ns re: tata ly moun said m s an hol ng one member f m axial m men il permitting axial movement of the other member, a rotary driving element rotatable in a single direetion, an l ctri cl ch or co l ng on of, s d mem= to. rotate with said rotary element, an elee= tri oteh f oupli said ther m mb r to rotate with said rotary element, electric brakes eaeh for holding one of said screw and nut members from rotation, and control means operable to s m ltaneously ene gize the lutc f r e her of said members to rotate it, and energize. the brake f t e othe o d m s to hold it flQ j ro atio 9., In combination with rotatably mounted en ag ment a rota y drivin e nt, e tric cl. ell moans ior rotat g one of said screw members with said driving element, electrio olutoh means for rotatin t e th r or said mem e s ele c r k me s for di one oi said screw and nut members from rotation, eleotrio brake means for holding the other or said members from rotation, and control means opera le fo s m an s y energizin the clu ch means for either of said screw and nut members to rotate it, and energizing the brake means {or the other Of said members to hold it'fromrotation, said Gontrol means also operable to simultanee ously deenergize said clutch and rake means for both said screw and nut members to free both of said members.

10. In combination with rotatabl mounted screw and bu m mbers havin s rew-thr aded en a ement f r m i g n mem e ax a by rotatin the other member, .a rotary element, f r tatin said l m nt i ne irect on. a s rewsaetuating member connected to rotate with and move ax ally of said s w m mbe :s

r gtsactuating member connected to rotate with and move axially of said nut member, e le ctr e.-v ma netic clutch coils One for coupling said screw.- actuating member to turn with said rotary ele= merit and another for coupling said nut-actuat..-.. the member to rotate with said rotary element, eieetrom enet brake coils one for holding said screweaetuating member from rotation and the other for holding said nut-actuating member from rotation, and control means for said clutch and brake coils.

11. In combination with a jack screw omprising rotatably mounted screw and nut members having screw-threaded engagement a spool rotatable about said jack screw and having annular flanges at opposite ends, means for rotat ing said spool, a screw actuating member connected to rotate with and move axially of said screw and having an annular flange adjacent one end flange of said spool, a nut-actuating member connected to rotate with and move axially of said nut and having an annular flange adjacent the opposite end flange of said spool, electromagnetic coils surrounding said spool one for causing said screw-actuating member to turn with said spool and the other for causing said nut-actuating member to turn with said spool, electromagnetic brakes surrounding said jack screw one adjacent to the flange of said screwaetuatin member and the other adjacent to the flange of said nut-actuating member, and control means for said clutch and brake coils for rotating one of said screw and nut-actuating members while holding the other of said screw or nut actuating members from rotation.

12. In combination with rotatably mounted screw and nut members having screw-threaded engagement for moving one member axially by rotating the other member, a rotary element, means for rotating said element in one direction, a screw-actuating member connected to rotate with and move axially of said screw member, a nut-actuating member connected to rotate with and move axially of said nut member, electromagnetic clutch coils one for coupling said screwactuating member to turn with said rotary element and another for coupling said nut-actuating member to rotate with said rotary element, electromagnet brake coils one for holding said screw-actuating member from rotation and the other for holding said nut-actuating member from rotation, and control means for said clutch and brake coils comprising means operable to energize the clutch coil and deenergize the brake iii) coil for either of said screw and nut-actuatin members, and means for simultaneously deenergizlng all of said clutch and brake coils.

13. In combination with :a jack screw compris- 8 screw and nut members having screw threaded engagement, means rotatably mounting said members and holding one member from axial movement while permitting axial movement of the other member, an annular driving element rotatable about said jack screw, means for rotating said driving element, a screw-actuatin member connected to rotate with and move axially of said screw, a nut-actuating member connected to rotate with and move axially or" said nut, electric clutch means carried by said driving element, one for causing said screw-actuating member to turn with said driving element and the other for causing said nut-actuating mechanism to turn with said driving element, electric brakes surrounding said jack screw, one adjacent to said screw-actuating member and the other adjacent to said nut-actuating member, and control means for said clutch means and brakes for causing rotation of one of said screw and nut-actuating members while holding the other of said screw or nut-actuating members from rotation.

FREDERICK G. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 885,945 Moore Apr. 28, 1901 1,398,978 Smith Dec. 6, 1921 1,416,182 Farmer May 16, 1922 1,819,697 Bondette Aug. 18, 1931 1,847,693 Kindervater Mar. 1, 1932 2,315,110 Dornier Mar. 30, 1943 2,383,901 Werner Aug. 28, 194,5 

